hello guys ,, i have a question about potentiometers,,lets say that we have 3 wires potentiometer ,first is 5 volt ref second signal wire and third is grownd,,,,,what happend if we have open ground and we read 5 volts in signal wire, because we have no voltage drop,,can that cause highter RPM because computer is reading hight voltage and is thinking that we are in WOT and is adding fuel ? can this happend?
Do you have a specific year make and model in mind?
I guess it depends on the logic in the pcm and how heavily it weighs the tps in the fuel strategy.
I would expect some kind of MAF/MAP/TPS correlation code to set and likely some other symptoms, (possibly even a no start), but I'm curious to see what others think.
Engine computers are pretty smart these days it would likely flag an out of range and go to a backup strategy which may or may not work With MAP engines most of the fueing is done on manifold vacuum and RPM with correction by the 02 sensor.
With MAF engines the the airflow and RPM the main input,
TPS is mainly for transients to avoid going lean when the throttle is floored. Of course with a lot of manufacturers 5v on the TPS signal wire when cranking would result in going into clear flood mode.
However ECU 's for racing and other off road like the Megasquirt are an exception they tend to be setup to work on RPM and throttle angle.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
i dont have any i am thinking vehicles up to 2004 that use varible rezistor ,not old ones who pontentiometer is just a swich ,,12 or 0 volts , on or off
so ,,u think ,that if we have open grownd ,,signal wire fixed 5 volts,pcm before adding fuel it looks map or maf sensor to know if this tps sensor is realy WOT or its a open ground that cause fixed 5 volts in signal wire.
I'm with Noah and Andy on this one. I'd expect the PCM to see 5.0V and set some kind of circuit or correlation code, and possibly start ignoring that input. How well the vehicle runs in that condition depends on the YMM, and the programming at work. :lol: GM's seem to do just fine without a main input, but Nissan's and Toyota's can really struggle.
I was working on a drive by wire today which of course has potentiometers working in opposite directions for exactly that reason.
MAF sensors on the BMW diesels are an interesting case with regard to backup strategies.
If the sensor is out of spec the engine will be way down on power but no fault code.
Disconnect the sensor and the engine runs better up to 3,000 RPM but but generates a fault code.
Biridge the sensor signal wire to 5v it flags a fault code but uses a different back-up strategy and pulls like a train up to 4,000 RPM
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
